The RC 35 contains the 1.5" large dynamic element of the PR 35 which produces a wide frequency response, natural vocal articulation, and high rear rejection from the sides and rear. The Heil replacement capsules are interchangeable with any of the screw-on type handheld transmitters that receive a 31.3mm/pitch 1.0mm. Some handheld transmitters have a .035-inch hexagonal-head set screw to secure the microphone capsule. If your transmitter has that, loosen the set screw in the handle of the microphone transmitter before attempting to unscrew the original capsule. Holding the bottom of the transmitter simply unscrew the original capsule turning it counterclockwise. Carefully remove. The three conductor contact board disconnects the contacts. Avoid touching or damaging the gold-plated contacts on the transmitter or the contact board.